Abstract

The outer membrane is the fi rst layer of the cell envelope of Gram-negative bacteria. This fragment of the cell envelope is built of phospholipids in the internal part and mainly of lipopolysaccharides in the external part. Lipopolysaccharide (LPS, endotoxin) is a thermostabile component consisting of three parts which differ in chemical structure and biological activity. LPS contributes greatly to the structural integrity of bacteria and protects them from host immune defenses. This review explains what makes this LPS leafl et an effective barrier to permeability and describes the pathways of biosynthesis and the assembly of the hydrophobic domain, known as lipid A, a core oligosaccharide, and the distal polysaccharide (O-antigen).

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